The present invention relates to deinking methods and compositions for waste paper and particularly to washing ink removal methods and compositions for recycle mills that use less sizing agents to produce paper having increased brightness and reduced effective residual ink concentration (ERIC).
The paper industry has been practicing wastepaper recycling to regenerate usable cellulosic fiber for paper making for many decades. In these processes, ink is removed from the wastepaper pulp using a suitable deinking composition. By controlling the deinking process, a recycling mill can affect the properties of the paper such as the brightness and can improve the usability of the cellulosic fiber for paper manufacturing.
There are two major types of deinking methods or practices, namely flotation/washing combination deinking and wash deinking. Flotation/washing combination deinking refers to a deinking process wherein the ink released by the deinking composition is separated from the cellulosic fibers primarily through the flotation devices or flotation cells of the recycling process prior to passing the pulp through washing stages (e.g. throuh washers). Wash deinking, on the other hand, refers to a deinking process wherein the ink released by the deinking composition is separated from the cellulosic fibers primarily in the washing stages.
Many deinking compositions have been developed specifically for wash deinking processes. In particular, various types of surfactants have been described as effective deinking agents. These surfactants include alkyl phenol alkoxylates, alpha olefin sulfonates, and aliphatic alcohol alkoxylates, as well as many other nonionic and anionic surfactants and mixtures of surfactants and other chemical agents. Generally, all of these compositions are required to have fluidity at room temperature for ease of feeding.
Conventional deinking compositions for wash deinking processes have been directed to improving deinking performance only, and particularly directed to removing ink from pulp to produce pulp with acceptable brightness for papermaking. There is a need to further improve the brightness of the paper pulp produced by wash deinking processes.
Furthermore, conventional deinking compositions significantly increase the water absorbency of paper and thus do not provide the amount of water repellency desired for certain types of paper such as recycled newsprint. As a result, paper made from wash deinking processes that use conventional deinking compositions has poor press room performance in the printing facility due to the extreme water absorbency of the paper. To improve the press room runability, paper manufacturers have had to use large amounts of a sizing agent, such as alkyl ketene dimer (AKD), in the manufacture of the paper to improve the water resistance (size) of the paper. Unfortunately, however, using large amounts of sizing agents results in the deposition of sizing agents on paper machinery, which is a significant problem in the recycled newsprint industry. In particular, because of the deposition of sizing agents on paper machinery, the paper machinery must be cleaned on a frequent basis thereby affecting the runability of the paper machinery. Moreover, the excessive use of sizing agents also impacts the coefficient of friction, which can cause problems in the paper such as crepe wrinkles, bursts and telescoping. Therefore, there is a need in the art to produce a deinking composition that reduces the amount of sizing agents needed to produce paper having high water repellency.
The present invention is a deinking method and composition that overcomes the problems associated with conventional deinking compositions. The deinking method and composition uses at least 50% by weight based on the total weight of surfactants of non-ionic, C16 to C25 aliphatic, monohydric alcohol alkoxylates having 14 to 40 moles of ethylene oxide per mole of alcohol and 0 to 10 moles of propylene oxide per mole of alcohol. It has been discovered that using deinking compositions to deink wastepaper pulp wherein the surfactants primarily include the C16 to C25 aliphatic alcohol alkoxylates of the invention unexpectedly produces paper having increased brightness and significantly decreased effective residual ink concentration (ERIC). Furthermore, it has also been discovered that using these C16 to C25 aliphatic alcohol alkoxylates to deink wastepaper pulp unexpectedly produces paper that requires a substantially lower amount of sizing agents to produce paper having acceptable levels of water repellency. Therefore, the deinking composition of the invention can be used in industries such as the newsprint industry with reduced sizing aent deposition on the machinery and thus increased paper machine runability. Furthermore, the deinking composition of the invention produces low levels of foaming as is desired in wastewater deinking processes.
The present invention comprises a deinking composition comprising one or more surfactants, the surfactants including at least 50% by weight, preferably at least about 70% by weight, and more preferably at least about 80% by weight based on the total weight of surfactants of non-ionic, C16 to C25 aliphatic, monohydric alcohol alkoxylates having 14 to 40 moles of ethylene oxide per mole of alcohol and 0 to 10 moles of propylene oxide per mole of alcohol. In one preferred embodiment of the invention, the surfactants in the composition consist essentially of non-ionic, C16 to C25 aliphatic, monohydric alcohol alkoxylates having 14 to 40 moles of ethylene oxide per mole of alcohol and 0 to 10 moles of propylene oxide per mole of alcohol. Preferably, the aliphatic alcohol alkoxylates of the invention are C16 to C18 aliphatic alcohol alkoxylates. For the C16-C25 aliphatic alcohol alkoxylates of the invention, the average number of ethylene oxide groups per alkoxylate molecule is preferably from about 16 to about 30 and the average number of propylene oxide groups per alkoxylate molecule is preferably from 0 to about 6. The C16-C25 aliphatic alcohol alkoxylates of the invention can be saturated or unsaturated. Preferably, the C16 to C25 aliphatic alcohol alkoxylates are saturated and have the formula:
Rxe2x80x94Oxe2x80x94(CH2xe2x80x94CH2xe2x80x94O)nxe2x80x94(CH2xe2x80x94CH(CH3)xe2x80x94O)mxe2x80x94H
wherein R is a straight chain or branched chain C16-C25 alkyl group, n is from 14 to 40 and m is from 0 to 10. More preferably, the C16-C25 aliphatic alcohol alkoxylates of the invention are straight chained. The C16-C25 aliphatic alcohol alkoxylates of the invention are preferably based on primary or secondary alcohols, and are more preferably based on primary alcohols. The deinking composition of the invention can further include from 0 to about 30% by weight of one or more fatty acids based on the total weight of surfactants. Preferably, the fatty acids are C8 to C20 fatty acids and can be selected from the group consisting of lauric acid, oleic acid, stearic acid, tall oil fatty acid, tallow fatty acid, coconut fatty acid, and mixtures thereof.
The present invention further includes a process for deinking wastepaper comprising the steps of contacting wastepaper pulp with the deinking composition discussed above. The surfactants (including the C16 to C25 aliphatic alcohol alkoxylates of the invention) are preferably present in the deinking composition in an amount from about 0.3% to about 0.7% by weight based on the oven-dry weight of the wastepaper pulp. In addition, the wastepaper pulp is preferably contacted with the deinking composition at a pH of from greater than 7 to about 10. The resulting wastepaper pulp can be used to make paper having increased brightness and low effective residual ink concentrations. In addition, in industries that use sizing agents to produce paper such as the recycled newsprint industry, the wastepaper pulp can be used to make paper having good water repellency without using large amounts of sizing agents.
These and other features and advantages of the present invention will become more readily apparent to those skilled in the art upon consideration of the following detailed description, which describes both the preferred and alternative embodiments of the present invention.